Some Basic concepts of chemistry
Frequently Asked Questions
Chemistry is the branch of science that studies composition, structure, properties, and transformations of matter.
Matter is anything that has mass and occupies space.
The SI unit is mole (mol).
One mole contains \(6.022\times10^{23}\) entities.
\(N_A = 6.022\times10^{23}\,mol^{-1}\).
\(1\,u=\frac{1}{12}\)th mass of one \(^{12}C\) atom.
Average mass of atoms relative to \(1/12\)th of \(^{12}C\).
Sum of atomic masses of all atoms in a molecule.
Sum of atomic masses in an ionic compound.
Molar mass \(=\frac{\text{Mass}}{\text{Moles}}\).
Mass of one mole of substance in g mol\(^{-1}\).
\(n=\frac{m}{M}\).
Mass percent of each element in a compound.
\(\%\text{element}=\frac{\text{mass of element}}{\text{molar mass}}\times100\)
Mass is neither created nor destroyed in a chemical reaction.
A compound always contains elements in fixed mass ratios.
Reactant consumed first, limiting product formation.
Reactant left unconsumed after reaction completion.
Quantitative relationship between reactants and products.
Simplest whole-number ratio of atoms.
Actual number of atoms in a molecule.
\(\text{Molecular formula}=(\text{Empirical formula})_n\)
\(n=\frac{\text{Molecular mass}}{\text{Empirical formula mass}}\)
Amount of solute per unit volume of solution.
\(M=\frac{\text{moles of solute}}{\text{volume in litres}}\)
Moles of solute per kg of solvent.
\(m=\frac{\text{moles}}{\text{kg solvent}}\)
Ratio of moles of component to total moles.
\(X_A=\frac{n_A}{n_A+n_B}\)
Gram equivalents per litre of solution.
\(\rho=\frac{m}{V}\)
\(M=\frac{\rho\times1000}{M_r}\)
Digits conveying measurement precision.
Non-zero digits significant; trailing zeros without decimal not significant.
Method using unit conversions to solve problems.
\(PV=nRT\)
\(8.314\,J\,mol^{-1}K^{-1}\)
Mass that reacts with or replaces 1 g H or 8 g O.
Quantitative analysis based on mass measurement.
Quantitative analysis using volume of solutions.
Process to determine concentration using standard solution.
Highly pure compound used to prepare standard solution.
Amount of product formed.
Maximum possible yield from given reactants.
\(\%\text{yield}=\frac{\text{actual}}{\text{theoretical}}\times100\)
Parts per million: \(10^{-6}\) fraction.
Closeness to true value.
Reproducibility of measurements.
Estimated range of measurement error.
\(6.022\times10^{23}\) atoms.
\(n=\frac{18}{18}=1\) mol.
\(0.5\times44=22\) g.
22.4 L (approximate school value).
Numerical factor before chemical species.
Equalizing atoms on both sides of reaction.
Substance consumed in reaction.
Substance formed in reaction.
Identification of constituents.
Determination of amount of constituents.
It connects atomic scale to laboratory scale for calculations.
